VILLA GARZON, Colombia -- Colombia Monday resumed spraying herbicides on illegal crops used to make cocaine along the country's border with Ecuador, a move opposed by Ecuador's incoming president.

The fumigation sets up a possible diplomatic conflict between Colombian President Alvaro Uribe, a conservative ally of Washington, and Ecuador's President-elect Rafael Correa, the leftist economist who won last month's election and is set to be inaugurated in January.

Correa says the spraying damages the natural environment and health of peasants on Ecuador's side of the border. The Uribe government claims none of the herbicides being sprayed on more than 10,000 hectares of Colombian coca fields near the border fall on Ecuadorean territory.

Colombia's U.S.-financed spraying along the 366-mile border between the countries was suspended 11 months ago amid Ecuadorean complaints that Colombia was violating its sovereignty in its fight against drug-smuggling rebels.

Colombia has been fighting a Marxist guerrilla insurgency for more than 40 years. The rebels fund their operations with proceeds from Colombia's multibillion-dollar cocaine trade.

"With the technical aspects we are applying, there will be no problem," he said, noting that the suspension of spraying had allowed coca growers to expand their fields.

Correa disagrees, saying the coca eradication will have to be done by hand.

"We understand Colombia's problem, but they will have to eradicate coca fields by foot. They cannot spray by plane because that gets into the Ecuadorean side and harms our crops," Correa told Monday's edition of Quito's "El Comercio" newspaper.

Colombian police say manual eradication is too slow, too expensive and dangerous for workers sent out to pull up coca plants.

Colombia has received billions in U.S. aid since 2000 aimed in part at combating the guerrillas, who Uribe says are responsible for the coca plantations near Ecuador.